68 occurring mixed with the typical plants. It is readily dis tinguished

68
BRITISH DESMIDIACE2E.
occurring mixed with the typical plants. It is readily dis­
tinguished from the typical form by its small size and exactly
cylindrical cells, which are not attenuated towards the apices.
4. Netrium interruptum (Breb) Liitkem.
(PI. V I I , figs. 1, 2.)
Penium interruptum Breb. in Balis' Brit. Desm. 1848, p. 151, t. 25, f. 4 j
De Bary, Conj. 1858, p. 42-44, 46, 73, t. 5, f. 1-4; Arch, in Pritch.
Infus. 1861, p. 751, t. 3, f. 45; Eabenh. Flor. Europ. Algar. 1868, III,
p. 119; Delp. Desm. subalp. 1877, p. 79, t. 15, f. 1-9; Wolle, Desm.
U.S. 1884, p. 35, t. 5, f. 14, 15 ; Cooke, Brit. Desm. 1886, p. 41, t. 16,
f. 2 ; Hauptfl. Zellm. u. Hiillgallerte Desm. 1888, p. 101, t. 3, f. 61;
West, Alg. W . Ireland, 1892, p. 127; Boy & Biss. Scott. Desm. 1894,
p. 59 (sep.) ; Nordst. Index Desmid. 1896, p. 148; West & G. S. West,
Alg. S. England, 1897, p. 479; Alga-fl. Yorks. 1900, p. 45 ; Alg. N.
Ireland, 1902, p. 21,
Closterium (Netrium) interruptum Reinsch, Algenfl. Frank. 1867, p. 185.
Netrium interruptum (Breb.) Lfitkem. Zellniembr. Desmid. 1902, p. 407.
Cells large, 4-6 times longer than their diameter, not
constricted, cylindrical, near each extremity becoming
suddenly conical, apices obtusely rounded; chloroplasts four, two in each semicell, median ones cylin­
drical, apical ones conical, each chloroplast with abont
eight longitudinal plates, free margins of plates entire ;
apical A^acuole conspicuous and containing a solitary
moving granule.
Zygospore unknown.
Length 220-320/x; breadth 37—64 fi.
ENGLAND.—Cumberland ! Westmoreland! N. Yorks !
Lancashire! Cheshire (Boy). Warwick (Wills). Sussex
(Balfs).
Surrey! Hants (Boy).
Cornwall! (Rolfs).
WALES.—Capel Curig ! (Coolce
Wills), Llyn Idwal,
Llyn-y-cwm-ffynon, and near Dolbadarn Castle, Car­
narvonshire !
SCOTLAND.—Ross, Inverness !, Aberdeen, Kincardine,
Forfar, Perth! (Boy Sf Bissett).
Lewis, Outer
Hebrides!
IRELAND.—Near Westport, Mayo ! Loughs Creggan
and Aunierin, Galway! Dublin and Wicklow (Archer).
Slieve Donard, D o w n !
Geogr. Distribution. — France. Germany. Austria.